There's nothing more heart-warming and endearing than a plucky husband-and-wife restaurant team who'll do backflips to please. And Alejandro Calleja and Sandra Lorenzo are just the sort of salt-of-the-earth, hard-working couple you really want to see succeed.

Having come here from Buenos Aires about three years ago with some Argentinian restaurant experience, this charming Catalan couple figured that opening Cambalache was an obvious next step. Alas, from las Pampas to the tundra, something clearly got lost in the translation.

How fitting that they chose to name their quaint eatery Cambalache, a Spanish word commonly used to describe chaos – a quality unfortunately shared by the wildly uneven food coming out of this kitchen. Located at what was for decades The Barmalay, Cambalache – which still looks much like The Barmalay inside, minus the armada of Russian tchotchkes – has transformed the once popular Russki resto into just one more T.O. tapas bar.

But this tapas is being touted as the real deal, with a whopping list of 45 meat, seafood and veggie items ($4.50 to $13) to choose from, much of it, sadly, disappointing. Starting on a good note, lamb meatballs ($8) couldn't be more beguiling. Pillowy-soft and juicy morsels, they're flattered by a thick, sweet tomato sauce that boasts an irresistible homemade quality. So, too, is a sophisticated, slightly thickened sherry sauce that spices up slices of mild chorizo sausage ($7.50). And keep those classic tango partners – manchego cheese ($6.50) and quince paste – a comin'.

But store-bought cheese, sausage and quince membrillo don't truly reflect a kitchen's gastronomic mettle, as the rest of the house-made dishes reveal a puzzlingly uneven hand. Like stringy spinach ($6) sautéed with raisins and pine nuts. Or pedestrian mushroom caps stuffed with an under-seasoned mixture of minced chorizo, onions, peppers and cheese ($8).

Crisp mussels ($7.50) are merely baked bivalves entombed in soggy breadcrumbs. And although classic shrimp in garlic olive oil ($7) are a classic, they're not properly deveined. (Really, who wants to eat shrimp poo?)

But the biggest misfire comes with the paella, the barometer of success in any Spanish kitchen. Big enough to feed four toreadors, the paella de mariscos ($38) is soggy with underseasoned (hello, saffron, are you there?) and overcooked rice, chockablock with plump but off-putting metallic-tasting scallops, overcooked shrimp, rubbery squid and miniscule clams and mussels.

The kitchen does redeem itself with revuelto de gramajo ($6.50), a scrumptiously loose toss of eggs, potatoes and strips of ham. Perhaps better appreciated at brunch, this deconstructed Western omelette is a crowd-pleaser. The cod empanadas are also brunch-worthy ($6.50); not your traditional turnover, these house-made mini-quiches are addictive. And desserts deliver with a creamy crème caramel ($5) along with a custard-heavy bread pudding ($4.50).

We hesitate to cast aspersions on the well-meaning offerings of a hard-working couple, but there's little excuse for mediocre food, especially in the case of a shockingly priced paella. Shifting focus to more inventive tapas offerings and ridding the menu of its less than authentic fare can take Cambalache closer to the culinary heart and soul of Spain.